When inserting a needle through tissue e.g. for sampling of an organ the needle often must be pushed through tissue having different inserting resistance due to different softness of the tissue.
A so-called Veress needle is a special needle used in laparoscopic surgical procedures. A conventional Veress needle consists of a hollow outer cannula ground obliquely to a sharp point at a distal end, and terminating in a plastic housing at the opposite proximal end. Enclosed within the outer cannula is a hollow tube that has a blunt tip at its distal end (common to the sharp tip of the outer cannula), and that is axially spring-biased in a distal direction by a spring contained in the plastic housing. When no force is applied to the distal end to resist the penetrating point, the spring bias forces the hollow inner tube to protrude just beyond the sharp tip of the outer cannula, obscuring the sharp tip and thereby protecting underlying organs from damage. When a force which overcomes the spring bias is applied to its distal end, as when the Veress needle is being pushed through a patient's abdominal wall, the inner tube is driven back within the outer cannula, exposing the sharp needle tip.
In the following, for illustrative purposes a few examples of documents within the field of Veress needles are cited.
WO-2013/173617 relates to a medical device encompassing a Veress needle with a mechanism for optionally extending, locking and unlocking its central tubular stylet.
In WO-2014/028428 a Veress needle is disclosed including an outer needle having a shaft and a sharp distal point. The sharp distal point and a distal portion of the shaft are configured to penetrate tissue. A spring-loaded, inner cannula is disposed in the outer needle. The cannula has a dull tip and a gas exit aperture is formed near a distal end of the cannula. The outer needle has an outwardly expandable portion located on the distal portion of the shaft.
Thus, one central feature of the Veress needle is that when the needle assembly penetrates soft tissue the stylet is in its distal position due to the spring-bias from the spring member. Thereby the tissue is less harmed because the blunt distal end is in its distal position “protecting” the sharp distal end of the cannula.
Other types of needle assemblies have been described that also use spring-biased members. One such assembly is described in US Patent Application 2003/0130621A1, which discloses a spinal needle system for entry into the epidural space. Another assembly is described in U.S. Pat. No. 5,685,852, which shows a needle assembly for epidural access comprising a hollow outer cannula with a sharp distal tip and a hollow blunt-ended stylet mounted within the cannula such that it is spring-biased to extend distally of the outer cannula.
Based upon the general knowledge of the Veress needle and other needle assemblies the inventor has identified further applications of the technique.
The object of the present invention is to achieve an improved needle assembly in the sense that it may be applied for different purposes and configured to be used in tissue having different properties.
In addition the needle assembly relieves the patient discomfort in that less manipulation is required when performing standard procedures.